I also had a problem with an eagle eye triggering falsely and thought it was from sunlight.
Turns out the eagle eye was facing the east side of my house (California) and in the morning when the sun was hitting the house, a wind chime hanging from the edge of the roof, between the eagle eye and the house, would move, and the change in the heat signature coming off the side of the house would "look like" motion to the eagle eye!
I was able to see this by soldering a test point on the output of the second op amp from the PIR sensor and watching the output, and seeing the wind chime move when the output would bounce around.
I solved this problem by masking off the top row of the lens with black tape.
I could have moved the wind chime as well, but didn't.
You might have something that is moving around (tree,bush,plant,etc.) that is between the eagle eye and another surface that is being heated by the sun.
The vertical pattern of the lens is very broad. I found that the top row looks up from (about) 10 degrees up to about 30 degrees up, the center row looks (almost) horizontal, and the bottom row looks (about) 10 to 30 degrees down.
Take a look at what is in the "view" of the eagle eye, and watch what moves when the eagle eye senses motion.